Pressure-Volume-Temperature Relations and Intermolecular Potentials for Methane and Tetrafluoromethane
1962; Elsevier BV; Linguagem: Inglês
10.1016/b978-1-4832-0083-5.50016-6
Autores Tópico(s)Advanced Physical and Chemical Molecular Interactions
ResumoTo provide an adequate basis for comparing the intermolecular behavior of methane and tetrafluoromethane, the P-V-T properties of these substances were determined with the same apparatus over the same pressure and temperature ranges. The experimental results expressed in terms of the sensitive residual quantity (PV/RT − 1)V and the virial coefficients B, C, and D are compared with results of other investigators. Intermolecular potential energy parameters of the Lennard-Jones (12,6), Lennard-Jones (28,7), modified Buckingham (6-Exp), Stockmayer, and Kihara potentials were evaluated from the experimental second virial coefficients. These parameters show that tetrafluoromethane is a much harder molecule than methane. The difference in hardness also was found in correlations of the experimental third and fourth virial coefficients made with the Lennard-Jones (12,6) potential. Qualitatively, the hardness or hardcore characteristic of tetrafluoromethane is explained by the high value of the bending force constant of the FCF bonds. The possible effects of the difference in hardness of methane and tetrafluoromethane on the calculation of their thermophysical properties with the aid of potential functions are considered.
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